1. Field of the Invention
The present invention relates to a display panel manufacturing method, a display panel manufacturing apparatus, and a display panel.
2. Description of the Related Art
A liquid crystal panel, as a main component of a liquid crystal display device, generally has a construction in which liquid crystal is disposed between a pair of glass substrates. TFTs as active devices, pixel electrodes and the like are provided on the inside surface of one of the glass substrates, while a color filter, an opposite electrode and the like are provided on the inside surface of the other of the glass substrates. An alignment film for alignment control of the liquid crystal molecules is formed on the surface of each glass substrate that is in contact with the liquid crystal.
A construction described in JP-A-2005-106997 is known as an example of a liquid crystal panel that includes alignment films.
Pinholes may be locally developed on the above-described alignment films for the following reasons.
(1) When a foreign substance slips in during an alignment-film-forming process so as to adhere to the alignment film, the alignment film is locally removed due to elimination of the foreign substance, resulting in a pinhole.
(2) When adhesion of an alignment film to its underlying base (e.g., pixel electrodes or an opposite electrode) is locally degraded, the alignment film material at the degraded portion is repelled during film formation, resulting in a pinhole.
(3) When an alignment film material for vertical alignment of liquid crystal molecules is used, adhesion of the alignment film to its underlying base is prone to degradation, which combined with the above (2) would cause a pinhole.
(4) When an alignment film having an uneven surface is formed by providing depressed portions or raised portions on the underlying base of the alignment film in order to control the alignment of the liquid crystal molecules, a larger area of the underlying base is covered with the alignment film, which combined with the above (2) would cause a pinhole.
If pinholes are locally developed on the alignment film for the above reasons, images cannot be displayed properly at those portions. Then, the alignment film should be completely removed and re-formed, depending on the sizes and/or positions of the pinholes. These problems result in increase in manufacturing cost.